Bilateral Discoid Medial Menisci

Abstract

Discoid medial meniscus is a relatively rare pathology of the knee joint, and bilateral cases are extremely rare. A high index of suspicion is necessary for diagnosis; only symptomatic knees should be treated surgically.

Bilateral Discoid Medial Menisci: A Case Report and Review of the Literature

“…There is an increased documented occurrence in Asian populations of Japan, India, and Korea compared with Caucasians, with rates reportedly up to 30% to 50% more frequent. 7 , 9 , 14 , 20 However, these values do not separate the discoid lateral meniscus from the discoid medial meniscus or the bilateral patterns that can occur. For discoid medial menisci, there would seem to be a predilection for male patients in the symptomatic population, with Liu et al (2016) reporting their cases in 85.7% men.…”

“…Since their discovery, controversy over the etiology involved in unilateral and bilateral discoid meniscus patterns have created many theories of their origin. 5 In 1948, Smillie et al, hypothesized that the discoid menisci shape is a normal developmental stage during embryological development and that persistence of this shape, owing to failure of absorption of the central meniscus during the fetal stage, leads to “congenital discoid meniscus.” 8 9 10 11 12 However, Weiner and Rosenberg (1974) provided evidence that as early as the 10th week of embryonic development, the cartilage of the knee has a shape that closely resembles that of an adult. 13 - 15 Weiner and Rosenberg attributed the changes in the discoid meniscus to congenital alterations in the formation of the tibial plateau that then may alter the meniscus structure.…”

“… 13 - 15 Weiner and Rosenberg attributed the changes in the discoid meniscus to congenital alterations in the formation of the tibial plateau that then may alter the meniscus structure. 9 , 10 , 14 - 16 Recent authors have also described flattening of the femoral condyles in the coronal plane of the knees concomitant with discoid medial meniscus, uncertain if the association is one of cause or effect. 12 Kaplan (1957) believed that discoid menisci were not present normally at birth but developed over time because of an abnormal mechanical motion from the absence of the posterior tibial attachment.…”

“…An analysis of these medial menisci found 10 were discoid (0.12%), with 1 patient (0.012%) having a BDMM pattern. 1 , 3 , 6 , 8 - 10 , 12 , 16 , 18 , 19 A meta-analysis conducted by Marchetti et al (2007) based on the collective surveys of 35,000 medial menisci patients, of which 32 discoid medial menisci (0.089%) were identified. Of these 32 discoid medial menisci, four knees from two patients were acknowledged as having BDMM for an incidence of 0.0056%.…”

“…However, the true rate of discoid medial menisci and the bilateral variant is likely higher because of its asymptomatic occurrence in most cases. 9 …”